// Copyright(c) 2015-present, Gabi Melman & spdlog contributors.
// Distributed under the MIT License (http://opensource.org/licenses/MIT)

#pragma once

#include <cassert>
#include "abel/log/common.h"


namespace abel {
namespace details {

ABEL_FORCE_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n,
                                           std::function<void()> on_thread_start)
        : q_(q_max_items) {
    if (threads_n == 0 || threads_n > 1000) {
        throw_log_ex("abel::thread_pool(): invalid threads_n param (valid "
                     "range is 1-1000)");
    }
    for (size_t i = 0; i < threads_n; i++) {
        threads_.emplace_back([this, on_thread_start] {
            on_thread_start();
            this->thread_pool::worker_loop_();
        });
    }
}

ABEL_FORCE_INLINE thread_pool::thread_pool(size_t q_max_items, size_t threads_n)
        : thread_pool(q_max_items, threads_n, [] {}) {}

// message all threads to terminate gracefully join them
ABEL_FORCE_INLINE thread_pool::~thread_pool() {
    ABEL_TRY {
        for (size_t i = 0; i < threads_.size(); i++) {
            post_async_msg_(async_msg(async_msg_type::terminate), async_overflow_policy::block);
        }

        for (auto &t : threads_) {
            t.join();
        }
    }
    ABEL_CATCH_ALL() {}
}

void ABEL_FORCE_INLINE thread_pool::post_log(async_logger_ptr &&worker_ptr, const details::log_msg &msg,
                                             async_overflow_policy overflow_policy) {
    async_msg async_m(std::move(worker_ptr), async_msg_type::log, msg);
    post_async_msg_(std::move(async_m), overflow_policy);
}

void ABEL_FORCE_INLINE
thread_pool::post_flush(async_logger_ptr &&worker_ptr, async_overflow_policy overflow_policy) {
    post_async_msg_(async_msg(std::move(worker_ptr), async_msg_type::flush), overflow_policy);
}

size_t ABEL_FORCE_INLINE thread_pool::overrun_counter() {
    return q_.overrun_counter();
}

void ABEL_FORCE_INLINE thread_pool::post_async_msg_(async_msg &&new_msg, async_overflow_policy overflow_policy) {
    if (overflow_policy == async_overflow_policy::block) {
        q_.enqueue(std::move(new_msg));
    } else {
        q_.enqueue_nowait(std::move(new_msg));
    }
}

void ABEL_FORCE_INLINE thread_pool::worker_loop_() {
    while (process_next_msg_()) {}
}

// process next message in the queue
// return true if this thread should still be active (while no terminate msg
// was received)
bool ABEL_FORCE_INLINE thread_pool::process_next_msg_() {
    async_msg incoming_async_msg;
    bool dequeued = q_.dequeue_for(incoming_async_msg, std::chrono::seconds(10));
    if (!dequeued) {
        return true;
    }

    switch (incoming_async_msg.msg_type) {
        case async_msg_type::log: {
            incoming_async_msg.worker_ptr->backend_sink_it_(incoming_async_msg);
            return true;
        }
        case async_msg_type::flush: {
            incoming_async_msg.worker_ptr->backend_flush_();
            return true;
        }

        case async_msg_type::terminate: {
            return false;
        }

        default: {
            assert(false);
        }
    }

    return true;
}

} // namespace details
}  // namespace abel
